Hitherto, washing of clothing has been carried out generally by immersing the clothing in a washing solution prepared by dissolving a detergent in cool water or hot water and mechanically stirring by means of a washing machine. Such a washing method of the type of immersing in water requires to use water and detergent in large amounts of 20 to 30 l water and 40 to 50 g the detergent per kg of the clothing, because the clothing should be completely immersed in the washing solution.
However, in the recent years, with an increase of population, water tends to be in short supply, and pollution of the quality of water caused by waste washing solution becomes a big social problem due to insufficient waste water disposal plants.